The present invention relates to the field of diffraction gratings.
For certain uses, it is desirable to select or specify the harmonic content of a diffraction grating. As an example, in a grating-based shearing interferometer it could be desirable to have the plus and minus first harmonics only. Those skilled in the art will recognize that a grating with plus and minus first orders only, has a true sine function amplitude transmission, and similarly will recognize that such a grating is difficult to fabricate because of the requisite continuously varying magnitude transmission and infinitely sharp phase transmission function transitions.
It is thus an object of the present invention to provide a method of designing a controlled harmonic grating (having both binary magnitude and phase transmissions) in which specified harmonics are enhanced and/or suppressed, to eliminate the above stated difficulties involved in fabricating continuous gratings such as true sinusoidal gratings.
It is a further object of the present intention to provide an easy method of fabricating this type of grating due to the binary constraints applied.
It is a further object of the present invention to fabricate a grating having a binary magnitude transmission function which may be conveniently created by means of applying metal, coated through etched photo resist, together with a phase function which may be created by the application of an appropriate phase retarding material, such as silicon dioxide, also deposited through a photo resist.